Device for applying and/or removing coatings on workpieces

ABSTRACT

A device and method for using the device for applyng and/or removing coating on workpieces are disclosed. The device comprises a medium conveying device and a container adapted to receive the workpieces. The container has an inlet line connected to a medium source, an outlet line connecting the container to a medium source, the medium source being positioned below the conveying device, and a control device which connects the inlet and outlet lines to the medium source. The conveying device is a vacuum pump incorporated in the outlet line of the container.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a device for applying and/or removing coatingson workpieces, said device having conveying means and a container(process chamber) for receiving the workpieces, an inlet line which isconnectable to at least one medium source and an outlet line connectingthe container to the medium source, said medium source disposed belowthe conveying means where the connection between the lines and themedium source is established by at least one control device which isconnectable to at least three different medium sources and disposedbelow the container.

In conventional devices of the type mentioned above and as described,for example, in German Patent DE 10 34 447 B or British Patent GB 893570 A, the medium is pushed into the process chamber. As a result, whenmedia are changed, deposits remain in the conveying device and mix withthe new medium. Thus, it is not possible to use these devices where ahigh degree of purity of the medium transported into the process chamberis required. A further disadvantage is that, if the lines are damaged,the media are conveyed to the outside under high pressure, due tooverpressure in the lines and the process chamber.

Based on the above state of the art, it is an object of this inventionto provide a device which operates without forming deposits and whichcan be used with incompatible liquids.

This object is attained in accordance with one embodiment of thisinvention wherein wherein the conveying means is a vacuum pump and isincorporated into the outlet line of the container (process chamber).

Accordingly, because the circulation of the liquid from the mediumsource to the container (process chamber) and back to the medium sourceis achieved by under negative pressure, at most an implosion may occurin the lines or reservoirs in the event of leaks. As a result, themedium does not reach the outside, but rather flows back into theassociated medium reservoir by itself. In addition, during operationthere are no noticeable disruptions of the operation, because switchingoccurs very rapidly. In this way, one continuous cycle is replaced byanother continuous cycle in extremely short time.

In accordance with one embodiment of this invention, the conveying meansis positioned above the medium sources. As a result all lines betweenthe container (process chamber) and the medium, as well as the controlmeans, for example radial or axial sliding valves, are completelyemptied if they are not under pressure and they are connected to therespective medium reservoirs so that medium can flow through them.

In accordance with another embodiment of this invention, at least oneopening for a holder supporting at least one workpiece is provided inthe wall of the container (process chamber). The holder has anelastically deformable sealing section which is connected under pressurewith the wall. In accordance with yet another embodiment of thisinvention, the opening is provided with a sheathing in the form of atruncated cone which tapers towards the interior.

This invention is applicable to and can be utilized, in particular, inthe field of medicine, and more particularly, in the dental field. Inembodiments of this invention suitable for such applications, thecontainer (process chamber) comprises a material which is resistant tothe media. Because the container (process chamber), is under negativepressure the plugs in the container do not require threads, it beingsufficient to place them in the openings after they have been suppliedwith the workpieces. Because of the negative pressure, a force directedtowards the interior of the container acts on the plugs and preventstheir separation from the container.

Located between the conveying device and the container (process chamber)is a magnetic valve (V) which, when opened, equalizes the pressure sothat the liquid can flow from the container (process chamber) and thelines into the appropriate medium reservoir without leaving a residue.Opening of the valve to the outside is regularly performed shortlybefore the end of one process step in which a particular liquid is used.When the valve has been closed again, a new and different medium flowsinto the container (process chamber). The plugs can be removed from theopenings at the end of the entire process. In accordance with anotherembodiment of this invention, an entire wall in the container comprisesa plate equipped with the plugs and workpieces and removable from thecontainer (process chamber), which is then connected with the container(process chamber).

In a device for making electrolytically producible coatings on metallicbodies, the surfaces of the portions of the workpieces extending intothe container (process chamber) are designed as a cathode or an anode,where an anode or a cathode is disposed opposite the workpieces and anelectrolyte flows between the electrodes. To ensure that the inflowingliquid sufficiently bathes the workpieces, a device which affects thedirection of flow of the liquid is disposed within the container(process chamber). In accordance with one embodiment of this inventionthe inlet line is connected to the bottom and the outlet line isconnected to the top of the container (process chamber), the devicecomprises two plates, disposed at a distance from the bottom and the topof the container (process chamber), which cover the bottom or the topexcept for a gap or a slit in the area of the wall supporting theworkpieces. This ensures that the incoming liquid flows along the insideof the wall supporting the work pieces and optimally bathes theworkpieces.

In accordance with another embodiment of this invention, the a device isconnected to an electrolyte reservoir as well as to pre-rinse and rinsewater reservoirs it is advantageous, if an ion exchanger for theregeneration of the rinse water is disposed in the pre-rinse and rinsewater reservoir. It is additionally preferred that two ion exchangerseach be disposed in each reservoir. Such an ion exchanger comprises ahollow body, removably connected to the inlet or outlet opening of thereservoir and having an inlet and outlet opening, where means forabsorbing ions are disposed between these openings. The advantage ofthis configuration is that the ion exchangers--once they are no longerfulfilling their function --can be removed from the reservoir andreplaced by fresh ones. In this case the user of the device does notcome into contact with any liquid.

This invention also relates to a method for applying and/or removingcoatings from workpieces with a device as previously described. Inaccordance with the process of this invention the workpieces aredisposed in the interior of the container (process chamber), theworkpieces are pre-treated, if required. The control device is actuatedso that an electrolyte or another chemical liquid flows through thecontainer (process chamber). After a defined coating has formed, thecontrol device connects the lines to a rinsing liquid which then flowsthrough the container (process chamber).

Some exemplary embodiments of the invention are schematically shown inthe drawings and will be described in detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a device for galvanizing in accordancewith one embodiment of this invention;

FIG. 2 is a schematic diagram of a container (process chamber), inaccordance with one embodiment of this invention;

FIG. 3 is a cross-sectional side view of a reservoir for a mediumsource, in accordance with one embodiment of this invention;

FIG. 4 is a schematic diagram of a container (process chamber) having ananode disposed outside of the container in accordance with anotherembodiment of this invention;

FIG. 5 is a schematic diagram of an anode in relationship to a workpiecein accordance with another embodiment of this invention; and

FIG. 6 a schematic diagram of a reservoir for a medium source inaccordance with another embodiment of this invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

In FIG. 1, a device for applying and/or removing coatings fromworkpieces 10 and 12 in accordance with one embodiment of this inventionis shown, having a container (process chamber) 14 which receivesworkpieces 10 and 12. An inlet line 16 is connected to at least onemedium source 18 and an outlet line 20 connects the container (processchamber) 14 to the medium sources 18, 19 and 21. Inlet line 16, outletline 20 and the medium sources 18, 19 and 21 are connected by a controldevice 24, in accordance with a preferred embodiment of this invention,a radial sliding valve.

The control device 24 is a valve comprising two circular disks 1 and 2,rotatable around a common axis in respect to each other. Control device24 is disposed below the container (process chamber) 14 and above themedium sources 18, 19 and 21. Inlet line 16 and outlet line 20 extendessentially vertically so that no deposits are formed in them. The inletline 16 and outlet line 20 can be connected to more than two reservoirs18, 19 and 21 by radial sliding valve 24. A negative pressure conveyingdevice 26 is incorporated into the outlet line 20. In accordance withone embodiment of this invention, conveying device 26 is a vacuum pump.Thus, the liquid is transported, for example, from the reservoir 18 intothe line 16 and from there into the container (process chamber) 14.Because there is negative pressure in the container (process chamber)14, the liquid flows through line 20 into the radial sliding valve 24and from there back into the reservoir 18.

FIG. 1 further shows two openings 30 and 32 for the holders 40 and 42supporting the workpieces 10 and 12 cut in the wall 28 of the container(process chamber) 14. The holders 40 and 42 have an elasticallydeformable sealing section secured under pressure to the wall 28. Thesheathing of the openings 30 and 32 is a truncated cone which taperstowards the interior of container. To use the device shown in FIG. 1 formaking electrolytically producible coatings on metallic bodies, thesurface of the section of the workpieces 10 and 12 extending into theinterior of the container (process chamber) 14 compromises a cathode oranode, while opposite of the workpieces 10 and 12, an anode 44 orcathode is disposed. The liquid flows between these two electrodes.

To assure that the liquid supplied through line 16 covers the workpieces10 and 12, a device 50, 52, which affects the direction of flow of theliquid 46, is disposed inside the container (process chamber) 14. Theinlet line 16 is connected in the bottom area of container, whichpreferably is funnel-shaped, and the outlet line 20 is connected in thetop area of the container (process chamber) 14. The device 50, 52affecting the flow of the liquid comprises two plates, disposed at adistance from the bottom 54 or the top 56 of the container (processchamber) 14, which cover the bottom 54 or the top 56 with the exceptionof gaps 60, 62, each said gap 60, 62 disposed in the wall area of thewall 28 supporting the workpieces 10 and 12.

FIG. 1 also shows a valve (V) incorporated in the line 20 as well asbetween the conveying device 26 and the container (process chamber). Thevalve (V), provided for ventilation is a magnetic valve arc is alwaysoperated when emptying the container (process chamber) 14 and returningthe liquid present therein to the appropriate reservoir 18, 19 and 21.In this manner, pressure equalization occurs in the container (processchamber) 14, so that the liquid can flow downwards through the inletline 16. It is not necessary to shut off the conveying device 26.

FIG. 2 shows, in accordance with another embodiment of this invention, aswirling device, propeller 3, disposed inside the container (processchamber) 14 to enhance the bathing of workpieces 10, 12 in the inflowingelectrolyte.

FIG. 1 and FIG. 3 show two ion exchangers 64 and 66 for regenerating therinse water disposed in the rinse water reservoir 19. The ion exchangers64 and 66 each consist of a hollow body, removably connected to thereservoir inlet opening 72 or reservoir outlet opening 70 of thereservoir (process chamber) 14, have an exchanger inlet and exchangeroutlet opening 74, 78 or 76 and 80. Means 82, preferably a resin, forabsorbing ions are disposed between these openings.

In accordance with one embodiment of this invention, a liquid havingions, for example water, flows through the exchanger inlet line 6 intorinse water reservoir 19 and into a hollow body 90 of first ionexchanger 66. This cylindrical hollow body 90 has a plurality ofradially oriented holes 91 and 92. The liquid flowing from the hollowbody 90 passes through ion-absorbing means 82 and reaches the interiorof the rinse water reservoir 19 through first exchanger outlet opening76. The liquid flowing through first exchanger outlet opening 76 intothe interior of rinse water reservoir is essentially free of one ofcations or anions. From there, the liquid follows into the interior ofsecond ion exchanger 64 through second exchanger inlet opening 78, whichis constructed essentially the same as the first ion exchanger 66 which,however, absorbs one of cations or anions not absorbed by first ionexchanger 66. Consequently the liquid flowing through exchanger outletline 7 has been freed of ions. When the ion exchangers 64 and 66 nolonger function, they are removed from rinse water exchanger 19 andreplaced by others.

The wall 28 of the container 14 may also be disposed as a magazine forblanks.

Thus, a significant feature of this invention is the fact that not onlylarge pieces, such as pipes of a length of several meters, but alsosmall articles, such as screws, rings or artificial teeth can be. Toprevent oxidation of the coating, it is possible to react theelectrolyte with, for example, nitrogen. Using additional devices, theelectrolyte may be swirled, for example, by stirring or ultrasound. Itis preferred to use non-soluble anodes or electrodes. It is also assuredthat no evaporation losses of the liquids take place.

When producing galvanic coatings of workpieces with uneven surfaces, thedistance between the anode and the cathode (workpieces) has a decisiveeffect on the thickness of the coating. Thickness in this case dependson the current density and the time of exposure. Because of nonuniformcurrent intensity at edges, recesses and bulges of the workpieces, thethickness of the coating is not quite uniform. This is because therecesses are at a greater distance from the anode than the front of theworkpiece facing the anode.

A partial solution is obtained by distancing the anode far enough fromthe workpieces that the depth of the recesses is infinitesimally smallin comparison to the distance of the anode from the cathode. However,this requires that the container be made larger, a distinctdisadvantage.

In FIGS. 4 and 5 it is shown that the length of the lines of electricflux 110 and 111 is very great, although the distance between the anode104 and the work pieces 10 and 12 is relatively short. The anode 104 ishoused in a receptacle 100, the distance of which from the workpiece 10is noticeably less than the length of the lines of electric flux 110 and111 between the anode 104 and the cathode 10. The receptacle 100 isdisposed outside of the container (process chamber) 14. In accordancewith one embodiment of this invention, receptacle 100 is a stretchedbody, the open side of which communicates with the container (processchamber) 14. A plurality of baffles 106 and 107 is disposed between theopen side 120 and the anode 104. The baffles 106 and 107 are in the formof guide plates, so that the lines of electrical flux 110 and 111 are inthe form of serpentines and meanders. Consequently, the length of thelines of electrical flux--measured from the anode 104 to the workpiece10--is increased such that the bottom 116, which is further away fromthe anode by a distance x, is approximately as far from the anode as thefront 115 of the workpiece 10. If the length of the lines of electricalflux is called d, that is, the length of the line of electrical flux 110from the anode to the front 115, and the length of the line of flux 110'is d+x, then d/d+x is approximately 1. The current intensity isapproximately as great in the bottom area 116 as in the front area 115,so that the thickness of the coating is approximately the same.

Screens 108 and 109 are provided for focusing the lines of electricalflux 110 and 111, so that the lines of electrical flux 110 and 111 leavethe aperture 120 with approximately the same density.

FIG. 5 furthermore shows that the anode 104 is surrounded bygrain-shaped particles 121, which may be of copper, nickel, gold,silver, chromium or the like. The particles 121 are housed in acollector 102, which communicates with the receptacle 100. Thereceptacle 100 and the collector 102 are made of one piece andessentially L-shaped, the lower portion of the collector 102 surroundingthe anode. In this way galvanic coatings are prepared by electrolyticdecomposition of metal salt solutions. Accordingly, it is possible toproduce a copper coating on the metallic object 10 by suspending theobject as a cathode in a copper sulfate solution and to employ an anodecomprising a plate which is surrounded by copper particles, for example,granulate, small spheres, etc. The Cu⁺⁺ ions migrate to the negativelycharged object and there form the layer, while the remaining acid ionsSO₄ ⁻⁻ free fresh Cu⁺⁺ ions from the Cu anode, so that the concentrationof the solution is maintained. The current density must be maintainedsufficiently low, to prevent the Cu coat from becoming porous andspongy. By using the granulate, the distance of the anode 104 from theworkpiece 10 is maintained constant, because the used-up granulatedisposed in the area of the bottom of the anode 10 can be replaced byfresh granulate, which extends as far as the cover 103.

Finally, FIG. 6 illustrates a reservoir 200 in accordance with anotherembodiment of this invention which approximately corresponds to thereservoir 19 according to FIG. 1. The essential difference between thereservoir 200 and the medium reservoir 19 is that the entire reservoir200 is designed as an ion exchanger, which can be connected to inletline 16 and outlet line 20 through the radial sliding valve 24 byconnections 212 and 214. The reservoir (ion exchanger) 200 has threefilters 202, 204 and 206, between which ion absorption material, forexample, a resin, for cations 208 or anions 210 is disposed. This ionexchanger 200 can be operated in either direction.

I claim:
 1. In a device for one of applying and removing coatings onworkpieces, having a conveying device and a container which receives theworkpieces, an inlet line connected to at least one medium source and anoutlet line connecting the container to the medium source, the mediumsource being disposed below the conveying device, where the inlet lineand the outlet line are connected to the medium source by a controldevice which is connectable to at least three different said mediumsources and disposed below the container,the improvement comprising, theconveying device (26) is a vacuum pump and is incorporated in the outletline (20) of the container (14).
 2. In a device in accordance with claim1, whereinthe inlet line (16) terminates in an area of a lowest point ofthe container (14).
 3. In a device in accordance with claim 2 furthercomprising means for continuously circulating at least one medium in aclosed cycle.
 4. In a device in accordance with claim 3,wherein a valve(V) is incorporated in the outlet line (20) between the conveying device(26) and the container (14).
 5. In a device in accordance with claim4,wherein means (3) for swirling are disposed in the container (14) bywhich said medium present in the container (14) can be swirled.
 6. In adevice in accordance with claim 5,wherein a wall (28) of the container(14) has at least one workpiece opening (30, 32) for a holder (40, 42)for at least one said workpiece (10, 12).
 7. In a device in accordancewith claim 6,wherein said holder (40, 42) for said workpiece (10, 12)has an elastically deformable sealing section secured under pressure tothe wall (28).
 8. In a device in accordance with claim 7,wherein asheathing of said workpiece opening (30, 32) is in a shape of atruncated cone, and tapers towards an interior of the container (14). 9.In a device in accordance with claim 8 further comprising an electrode,means for electrically charging said workpiece (10, 12), each of saidelectrode and said means for electrically charging said workpiece (10,12) connected to a voltage supply, and an electrolyte (46) flowingbetween said electrode and said means for electrically charging saidworkpiece (10, 12).
 10. In a device in accordance with claim 9,whereinat least one of said medium sources is an electrolyte reservoir, atleast one of said medium sources is a pre-rinse and rinse waterreservoir (19), and at least one ion exchanger (64, 66) for regenerationof rinse water is disposed in said pre-rinse and rinse water reservoir(19).
 11. In a device in accordance with claim 10,wherein two said ionexchangers (64, 66) are disposed in said pre-rinse and rinse waterreservoir (19).
 12. In a device in accordance with claim 11,wherein saidion exchanger (64, 66) comprises a hollow body, removably connected toone of a reservoir inlet opening and a reservoir outlet opening (70, 72)of said pre-rinse and rinse water reservoir (19) and having an exchangerinlet opening (74, 78) and an exchanger outlet opening (76, 80), andmeans (82) for absorbing ions disposed between said exchanger inletopening (74, 78) and said exchanger outlet opening (76, 80).
 13. In adevice in accordance with claim 12, wherein said electrode (104) ishoused in a receptacle (100) in communication with said container,whereby a distance of said electrode (104) from the workpiece (10) isless than a length of a line of electrical flux (110, 111) between saidelectrode (104) and the workpiece (10).
 14. In a device in accordancewith claim 13,wherein said receptacle (100) is disposed outside of thecontainer (14).
 15. In a device in accordance with claim 14,wherein saidreceptacle (100) is a stretched body having an open side (12) whichcommunicates with the container (14) and a plurality of baffles (106,107) are formed between a side (120) of said receptacle (100) and saidanode (104).
 16. In a device in accordance with claim 15,wherein saidplurality of baffles (106, 107) are in the form of guide platesproducing said line of electrical flux (110, 111) which is serpentine.17. In a device in accordance with claim 16,wherein said anode (104) issurrounded by a plurality of granulate-shaped particles (121) selectedfrom the group consisting of Cu, Ni, Au, Ag, Cr, Sn and mixturesthereof.
 18. In a device in accordance with claim 17,wherein saidplurality of granulate-shaped particles (121) are housed in a collector(102) which is in communication with said receptacle (100).
 19. In adevice in accordance with claim 18,wherein said receptacle (100) andsaid collector (102) are made of one piece and are essentially L-shaped,where a lower end of the collector (102) surrounds an electrode.
 20. Ina device in accordance with claim 1 further comprising means forcontinuously circulating at least one medium in a closed cycle.
 21. In adevice in accordance with claim 1,wherein a valve (V) is incorporated inthe outlet line (20) between the conveying device (26) and the container(14).
 22. In a device in accordance with claim 1,wherein means (3) forswirling are disposed in the container (14) by which a medium present inthe container (14) can be swirled.
 23. In a device in accordance withclaim 1,wherein a wall (28) of the container (14) has at least oneworkpiece opening (30, 32) for a holder (40, 42) for at least one saidworkpiece (10, 12).
 24. In a device in accordance with claim 1,wherein aholder (40, 42) for said workpiece (10, 12) has an elasticallydeformable sealing section secured under pressure to a wall (28) of saidcontainer (14).
 25. In a device in accordance with claim 1,wherein asheathing of a workpiece opening (30, 32) is in a shape of a truncatedcone, and tapers towards an interior of the container (14).
 26. In adevice in accordance with claim 1 further comprising an electrode, meansfor electrically charging said workpiece (10, 12), each of saidelectrode and said means for electrically charging said workpiece (10,12) connected to a voltage supply, and an electrolyte (46) flowingbetween said electrode and said means for electrically charging saidworkpiece (10, 12).
 27. In a device in accordance with claim 26,whereinan ion exchanger (64, 66) comprises a hollow body, removably connectedto one of a reservoir inlet opening and a reservoir outlet opening (70,72) of a pre-rinse and rinse water reservoir (19) and having anexchanger inlet opening (74, 78) and an exchanger outlet opening (76,80), and means (82) for absorbing ions are disposed between saidexchanger inlet opening (74, 78) and said exchanger outlet opening (76,80).
 28. In a device in accordance with claim 1,wherein at least one ofsaid medium sources is an electrolyte reservoir, at least one of saidmedium sources is a pre-rinse and rinse water reservoir (19), and atleast one ion exchanger (64, 66) for regeneration of rinse water isdisposed in said pre-rinse and rinse water reservoir (19).
 29. In adevice in accordance with claim 28,wherein two ion exchangers (64, 66)are disposed in said pre-rinse and rinse water reservoir (19).
 30. In adevice in accordance with claim 1, wherein an electrode (104) is housedin a receptacle (100) in communication with said container, whereby adistance of said electrode from the workpiece (10) is less than a lengthof a line of electrical flux (110, 111) between said electrode (104) andthe workpiece (10).
 31. In a device in accordance with claim 1,wherein areceptacle (100) is disposed outside of the container (14).
 32. In adevice in accordance with claim 1,wherein a receptacle (100) is astretched body having an open side (12) which communicates with thecontainer (14), and a plurality of baffles (106, 107) are formed betweena side (120) of said receptacle (100) and an anode (104).
 33. In adevice in accordance with claim 1,wherein a plurality of baffles (106,107) in a receptacle which communicates with said container are in theform of guide plates producing lines of electrical flux (110, 111) whichare serpentine.
 34. In a device in accordance with claim 1,wherein in areceptacle which communicates with said container is surrounded by aplurality of granulate-shaped particles (121) selected from the groupconsisting of Cu, Ni, Au, Ag, Cr, Sn and mixtures thereof.
 35. In adevice in accordance with claim 1,wherein a plurality ofgranulate-shaped particles (121) are housed in a collector (102) whichis in communication with a receptacle (100), said receptacle incommunication with said container.
 36. In a device in accordance withclaim 1,wherein a receptacle (100) in communication with said containerand a collector (102) in communication with said receptacle (100) aremade of one piece and are essentially L-shaped, where a lower end of thecollector (102) surrounds an electrode.